To know why time is not absolute, we must date back in time and have to see the evolution of theories regarding space and time. At first, Aristotle proposed that the natural state of a body is to be at rest and starts moving only when it gets acted upon by some external force. It followed that a heavy body should fall faster than a lighter one on to the Earth. Later it was proved wrong by Galileo,and Newton proposed his three laws on the basis of Galileo's experiments. He proposed that, the natural state of a body is not to be at rest but to be in uniform motion and only when it gets acted upon by some external force, It starts accelerating. It follows from Newton's laws that there is no unique standard of rest. Lets for instance, a train was moving past an electric pole standing tall along the embankment, at a speed of 70 mph, one could equally say that the pole was at rest and the train was in motion or the train was at rest and the pole was moving past at the rate 70 mph; we can't really say which one is at rest preferably. If for someone inside a train which is in motion, an object appears at rest, and it appears in motion for someone outside the train. This implies, we can't assign any event an absolute position in space. hence space is not absolute.
They came up with non absolute space but still it was believed that 'time' was completely independent from 'space' and that one can unambiguously measure the interval between any two events that happen in space. In 1676, Christensen Roemer came up with a significant discovery that light travels at a finite speed and he calculates it to be around 140,000 miles per second, However later Clerk Maxwell precisely measured it to be 186,000 miles per second. Whatever it is, It adds a significant implication that light travels at a finite and more importantly fixed speed.
Here comes the most interesting part, if light has to travel at some fixed speed, It must travel relative to something at rest and what could be that 'something'?
They came up with a shockingly interesting and imaginary space, 'Ether', supposedly presents everywhere and obviously, at rest.
Later scientists tried to measure the time taken for the light (from a fixed source) to reach an object that is moving towards it, in one instance and moving away from it in another instance. Shockingly, they measured the same 'time' in both instances.
At that stage Albert Einstein came up with his famous Theory of relativity, which implies that time is not absolute, obviously no need of ether anymore. A remarkable consequence of relativity is the way it has revolutionized our ideas of space and time. In Newton's theory, if a pulse of light is sent from one place to another, different observers would agree on the time that the journey took (since time is absolute), but will not always agree on how far the light traveled (since space is not absolute), Which implies that different observers would measure different speeds of light. In relativity, on the other hand, all observers must agree on how fast light travels. They still, however, do not agree on the distance the light has traveled (since no absolute space), so they must now also disagree over the time it has taken. In other words, the theory of relativity put an end to the idea of absolute time, which means that time measures between any two events in space by two identical clocks would not necessarily agree, even though they show the same.
We must accept that time is not completely independent from space, but is combined with it to form an object called space-time

Phi masons which are highly unstable particles decay pretty quickly, but when they are accelerated at the speed closer to light they lasts 30times longer, which means that time travel is possible if we can accelerate closer to light's speed

lets for instance, our physicists successfully built a track along the earth's circumference and designed a train that can accelerate closer to light's speed. If the train has to travel at the speed of light, it has to circle the earth 7 times in a second, that's something we can't even imagine..right, anyways we can't cross or even reach the light speed but can get closer enough to travel in time, closer in the sense 99.9% that of light's speed. As the train begins its journey and starts accelerating at the rate 99.9% that of light's speed, the time inside train starts flowing slowly when compared with the rest of the world. Their 1 week of travel inside train equals 100 years for us and they will unboard to see the future earth.

What if a child inside the train starts running, does the added speed cross the speed of the light ?

The answer is no, because as he gets closer to the speed of light he feels heavier and heavier and to reach that point he need infinite energy which is practically impossible.

The Apollo with a speed of about 25000 miles/hour is so far the fastest space vehicle. To travel in time, we need much faster and much heavier one, almost 2000 times faster.The design says, the initial acceleration of that massive ship is very small but picks up acceleration to reach half the speed of light in 2 years and 2 more years it reaches 90% that of light speed at that time, its would reach our nearest solar system ,Centurion. 2 more years, 99.9% and starts traveling in time. one day on board equals to a whole year on earth.To reach the edge of the galaxy all they need is just 80 years

Most of the time, we try through the right methods to solve wrong problems. Identifying the right problem is the challenging task and once we are through with this, then solving it becomes simple and easy.

Time is considered as fourth dimension with the other three dimensions being filled with space. Until now we all know how to travel in space. In the near future, it is more than a possibility that we can even travel in time. Time travel is no more a fantasy.three of the possibilities have been under consideration so far and im going to explain the first one herefirst possibility:Nothing in the world is so plain, lets take a snooker ball, if we can observe it more closely, we can notice wrinkles and holes on its surface. If we can go deeper and deeper down the smallest scale smaller than molecules,smaller than atoms we will land in to a place called quantum world. This is the place where worm holes appear at a size of around billion trillion trillionth of a cm. These infinitesimally small holes actually are gateways for our time travel.Scientists believe that these worm holes can be made to appear in large scale and if someone dares to dive into it, he might even travel back in time and reach a point in past. But lot of physicists been asking a question like if it happens that someone, lets say 'x' went in to past and kills his own self, who is 'x' then. It violates the fundamental law of universe. This is a major drawback and has its own serious consequences.But this is not the end, the other two possibilities are far more interestingsecond possibilityThis one stems from Einstein's theory of general relativity. GPS, which is formed by hundreds of satellites revolving around the earth explains this concept better.the atomic clock that is equipped inside them is so accurate that it just delays in the order of 10−9 seconds per day. Even being so accurate, it needs massive corrections at regular intervals along the orbit.the problem being time warp, which means that time being very linear acts non linearly at certain points in space.they even exist on earth. Giza pyramid, which weighs around 40 million tons is surrounded by time warp. somebody who stay closer to that experience relatively slower drift in time. For an observer who stays closer to Giza pyramid, outside world appears a bit hurried. If we really want to traveling time, we need something much more massive than Giza pyramid. Fortunately the center of our galaxy is equipped with a super massive Black hole on the order of hundreds of billions of solar masses. It can slow time more than anything in our galaxy. Time gets warped near the super massive blackhole because of its heavy gravitational pull. Lets say if our scientists had built a space ship tthat can reach the center of Milkyway and is set to orbit around the super massive blackhole, for every 60 min of orbit,crew inside the spaceship experience 8 min lag. Round and round they go the ship and crew travels in to future more swiftly. Their 5 days of orbit around the super massive blackhole almost equals 8 years on earth, and when they return they would see the future. Building a spaceship to orbit around such a massive blackhole, withstanding its massive gravitational pull is almost impossible, but there is one last and best hope of time travel...

Time,being the fourth dimension of our universe,is interconnected with the space(three dimensions)in a way that it cannot exist without space, and space cannot exist without time. This kind of relationship between time and space is called the spacetime continuum, which means that any event that occurs in the universe has to involve both space and time. According to Einstein's theory of relativity, time gets slower as we approach the speed of the light,and apparently that means time travel is possible,but the problem is if any object tries to approach the speed of the light ,its mass gets increased (E=mC^2) for the apparent reason that we try to provide more and more energy to increase the objects speed and as E(energy) directly proportional to m(mass),mass gets increased and that reaches infinite as the object reaches the speed of the light,which is practically impossible.so we can't travel in time,this is what some our physicists say.Its possible.. they say

anyways,theories are never been agreed so easily,there is always an other side and this is how it goes:there are some physicists who believe traveling faster than light(FTL) is possible and they say..

The Milky Way Galaxy, commonly referred to as just the Milky Way, or sometimes simply as the Galaxy, is the galaxy in which the Solar System is located. The Milky Way is a barred spiral galaxy that is part of the Local Group of galaxies. It is one of billions of galaxies in the observable universe. Its name is a translation of the Latin Via Lactea, in turn translated from the Greek Γαλαξίας (Galaxias), referring to the pale band of light formed by stars in the galactic plane as seen from Earth (see etymology of galaxy).

Some sources hold that, strictly speaking, the term Milky Way should refer exclusively to the band of light that the galaxy forms in the night sky, while the galaxy should receive the full name Milky Way Galaxy, or alternatively the Galaxy.However, it is unclear how widespread this convention is, and the term Milky Way is routinely used in either context.

The Andromeda Galaxy is a spiral galaxy approximately 2,500,000 light-years (1.58×1011 AU) away in the constellation Andromeda. It is also known as Messier 31, M31, or NGC 224, and is often referred to as the Great Andromeda Nebula in older texts. Andromeda is the nearest spiral galaxy to our own, the Milky Way, but not the closest galaxy overall. As it is visible as a faint smudge on a moonless night, it is one of the farthest objects visible to the naked eye, and can be seen even from urban areas with binoculars. It gets its name from the area of the sky in which it appears, the Andromeda constellation, which was named after the mythological princess Andromeda. Andromeda is the largest galaxy of the Local Group, which consists of the Andromeda Galaxy, the Milky Way Galaxy, the Triangulum Galaxy, and about 30 other smaller galaxies. Although the largest, Andromeda may not be the most massive, as recent findings suggest that the Milky Way contains more dark matter and may be the most massive in the grouping.The 2006 observations by the Spitzer Space Telescope revealed that M31 contains one trillion (1012) stars, more than the number of stars in our own galaxy, which is estimated to be c. 200-400 billion.While the 2006 estimates put the mass of the Milky Way to be ~80% of the mass of Andromeda, which is estimated to be 7.1 × 1011 solar masses,a 2009 study concluded that Andromeda and the Milky Way are about equal in mass.At an apparent magnitude of 3.4, the Andromeda Galaxy is notable for being one of the brightest Messier objects,making it easily visible to the naked eye even when viewed from areas with moderate light pollution. Although it appears more than six times as wide as the full Moon when photographed through a larger telescope, only the brighter central region is visible to the naked eye or when viewed using a binoculars or a small telescope.

According to many physicists, the primary goal of physics today is the grand unified theory. it is supposed to describe the four forces as different aspects of a same force. the four forces, gravity, electromagnetic force, strong nuclear force, weak nuclear force have to be established as single form at some point(energy level) that get branched later on in the evolution process(cooling of earth) after big bang scientists,indeed,successfully combined three of the forces other than gravity.the first two forces that got unified were electromagnetic force and weak nuclear force in the year 1967 by Abdus Salam and Steven Weinberg.

They suggested that there were other massive particles along with photon(EM force carrier) having same spin,that carry weak nuclear force, collectively called as massive vector bosons(W+,W-,Z0), and the way they got divided is explained by a property called spontaneous symmetry breaking,which means that,what ever appear to be a number of completely different particles at low energies are in fact found to be all the same type of particle,only in different states.all these particles behaves similarly at higher energies(around 100's of Gev) and the symmetry get broken at lower particle energies to form massive W+,W- and Z0 along with photons.

later it was found that the strong nuclear force which was carried by gluons get weaker at higher energies making quarks and gluons act freely. It creates a new hope,that there must be some energy level where gluons, photons and bosons all behave the same & they predicted that it must be around thousand million million Gev and it can't be proved as there are no such oscillators till date. they also predicted that quarks and electrons would behave the same at that grand unified energy level.

Now the process of unifying gravity along with the other three is going on...

these four forces are carried by their respective particles as listed belowgravitational force by gravitonselectromagnetic force by photonsstrong nuclear force by gluonsweak nuclear force by bosons

out of the four forces gravitational force is considered the weakest, and the strong nuclear force which is carried by gluons is considered the strongest.

Gravitational force

Gravitational force, the weakest of the four forces, is about 10-36 times the strength of the strong nuclear force.The messenger particle of gravitational force is the graviton. It has not been experimentally verified, mainly because it is extremely hard to find the smallest denomination of the weakest force. Recent calculations show that it will likely be massless.

And somehow scientists are trying to include this in to a grand unified theory, where they successfully included the other three ..

Electromagnetism

Its strength is a bit less than strong nuclear force, and unlike gravitational force, it has both attractive and repulsive nature and is of infinite range--like gravity.

If gravitational force is what responsible for keeping up our universe together, EM is responsible for keeping up electrons around nucleus(attraction force between nucleus and electrons).

It is the force that causes the interaction between electrically charged particles; the areas in which this happens are called EM fields, also known as B fields in physics classes.

The particle that carry electromagnetism is the photon, a massless particle that travels at a speed of 299 792 458 m/s or 299 972 km/s .

The Weak Nuclear Force

The weak nuclear force is one of the less familiar fundamental forces. It operates only on the extremely short distance scales found in an atomic nucleus. The weak force is responsible for radioactive decay. In actuality, it is stronger than electromagnetism, but its messenger particles (W and Z bosons) are so massive and sluggish that they do not faithfully transmit its intrinsic strength.

The Strong Nuclear Force

Like the weak force, its range is limited to subatomic distances. quarks which forms the protons and neutrons stick together through this force. this fprce is carried by gluons and is a massless particle, as it glues the quarks together,its called a gluon.gluons also acts on other glons and that is why, as the distance increases the force increases at subatomic level .

Attempts have been going on to unify all these four fundamental forces to form a grand unified theory, and had successfully unified the other three, excluding gravity. Hope they will succeed soon.

Dark matter and dark energy ,these two are the most interesting problems in world of astronomy.they dominate the universe like comprising almost 96 percent of mass and energy that exists in the universe.But noone knows what they are. It's tempting to consider them products of the same unknown phenomenon, something theorist Robert Scherrer suggests. The professor of physics at Vanderbilt University says "k-essence" is behind it all.Dark matter was invoked decades ago to explain why galaxies hold together. Given regular matter alone, galaxies might never have formed, and today they would fly apart. So there must be some unknown stuff that forms invisible clumps to act as gravitational glue.Dark energy hit the scene in the late 1990s when astronomers discovered the universe is not just expanding, but racing out at an ever-faster pace. Some hidden force, a sort of anti-gravity, must be pushing galaxies apart from one another in this accelerated expansion.Separate theories have been devised to try and solve each mystery.To explain dark energy, for example, theorists have re-employed a "cosmological constant" that Einstein first introduced as a fudge factor to balance the force of gravity. Einstein called the cosmological constant a great blunder and retracted it. Yet many theorists now are comfortable re-employing it to account for the effects of dark energy. But it does not reveal what the force is.Scherrer agrees two explanations might be necessary, but he's also bothered by that complexity.

"It is somewhat embarrassing to have two different unknown sources for the dominant forms of matter and energy in the universe," he said in an e-mail interview. "On the other hand, that may just be the way things are. We don't get to pick the universe we live in."To explain this, Scherrer invokes an interesting energy field called scalar field. It's a bit like an electric or magnetic field, with energy and pressure and a magnitude. But a scalar field has no direction. A scalar field is thought to have been behind inflation, the less-than-a-second period after the Big Bang when the universe expanded many billions of times before settling into a more reasonable rate of growth.Scherrer borrows from work by Princeton University's Paul Steinhardt, V. Slava Mukhanov at the University of Munich and Christian Armendáriz Picón of the University of Chicago, relying on a specific type of second-generation scalar field they envisioned called k-essence, short for kinetic-energy-driven quintessence.K-essence changes behavior over time in Scherrer's model, clumping early on to help form galaxies, and now forcing the universe apart. Right now, dark matter has a density that decreases as the universe expands, he explained, while dark energy has a density that stays constant as the universe expands."That means that at very early times, the dark matter 'piece' of the k-essence is the dominant one," Scherrer said. "As the universe expands and the density of the dark matter 'piece' of the k-essence decreases, it eventually falls below the density of the dark energy 'piece,' and the k- essence behaves more like dark energy.""Scherrer's model , not the first trying to tie dark energy and dark matter together ", was published July 2 in the online version of the journal Physical Review Letters.

drawback

Although Scherrer's model has a number of positive features, it also has some drawbacks. For one thing, it requires some extreme "fine-tuning" to work. The physicist also cautions that more study will be required to determine if the model's behavior is consistent with other observations. In addition, it cannot answer the coincidence problem: Why we live at the only time in the history of the universe when the densities calculated for dark matter and dark energy are comparable. Scientists are suspicious of this because it suggests that there is something special about the present era.

Leptons (the most famous being the electron), and quarks (of which baryons, such as protons and neutrons, are made) combine to form atoms, which in turn form molecules. Because atoms and molecules are said to be matter, it is natural to phrase the definition as: ordinary matter is anything that is made of the same things that atoms and molecules are made of. (However, notice that one also can make from these building blocks matter that is not atoms or molecules.) Then, because electrons are leptons, and protons and neutrons are made of quarks, this definition in turn leads to the definition of matter as being "quarks and leptons", which are the two types of elementary fermions. Carithers and Grannis state: Ordinary matter is composed entirely of first-generation particles, namely the [up] and [down] quarks, plus the electron and its neutrino. (Higher generations particles quickly decay into first-generation particles, and thus are not commonly encountered.)This definition of ordinary matter is more subtle than it first appears. All the particles that make up ordinary matter (leptons and quarks) are elementary fermions, while all the force carriers are elementary bosons. The W and Z bosons that mediate the weak force are not made of quarks or leptons, and so are not ordinary matter, even if they have mass. In other words, mass is not something that is exclusive to ordinary matter.

The quark–lepton definition of ordinary matter, however, identifies not only the elementary building blocks of matter, but also includes composites made from the constituents (atoms and molecules, for example). Such composites contain an interaction energy that holds the constituents together, and may constitute the bulk of the mass of the composite. As an example, to a great extent, the mass of an atom is simply the sum of the masses of its constituent protons, neutrons and electrons. However, digging deeper, the protons and neutrons are made up of quarks bound together by gluon fields (see dynamics of quantum chromodynamics) and these Gluons fields contribute significantly to the mass of hadrons. In other words most of what composes the "mass" of ordinary matter is due to the binding energy of quarks within protons and neutrons. For example, the sum of the mass of the three quarks in a nucleon is approximately 12.5 MeV/c2, which is low compared to the mass of a nucleon (approximately 938 MeV/c2).The bottom line is that most of the mass of everyday objects comes from the interaction energy of its elementary components.

All matter, including the atoms in our bodies, the air we breathe and the gas in the Sun is composed is combinations of fundamental particles that were created during the Big Bang and subsequent evolution of the Universe. Before giving an outline of the key stages in the formation of matter we need to review the fundamental particles and forces in the Universe.Fundamental particles, the building blocks of the Universe

Our current understanding of physics allows us to model events in the Universe nearly, but not quite back to the moment of the big bang. Significant developments in our understanding of the very early Universe are due to advances in high-energy particle physics and particle accelerators such as those at CERN. According to the "Standard Model" of particle physics we now know that all the matter around us is composed of combinations of only a few fundamental particles. These twelve particles fall into two families, quarks and leptons.

Quarks are the particles that group together to form hadrons. Hadrons made of three quarks in turn are called baryons. The most familiar baryons to us are the protons and neutrons that comprise the nuclei of the atoms in our bodies and the rest of the Universe. A proton comprises two up quarks and one down quark, whilst a neutron has two down quarks and only one up quark. If you study the following table you will see that quarks have charges that are fractions of the charge of an electron, e. Hence the overall or net charge of a proton = 2 × (+2e/3) - 1 ×(-1e/3) = +1e and the overall charge of the neutron is 0.

Leptons include three charged particles, the electron, muon and tau particle. Each of these has an associated neutrino particle that is neutral.

Together these twelve particles are the building blocks of matter. Interestingly though, each of them has a corresponding antiparticle. These differ only in having the opposite charge but have the same mass as the corresponding matter particle. These antiparticles collectively are known as antimatter.